We surveyed 10 Trojan 10.8 Meter (35’) boats on the market that were built from 1986 to 1989. All appeared to be and claimed to be in good condition. Not surprisingly the gas engine-powered boats that were 1986 were priced on the low side, but the lowest one of all -- $39,900 – was being heavily discounted for quick sale because of a divorce (happens all the time).

“Boat A” is actually the average of three gas-powered Trojan 10.8 Meters at the low-end of the asking range. All were gas boats. “Boat B” is the average of three boats at the high end of the asking range. One was diesel powered (DDAs) and the other two were gas powered. All were built within 4 years of each other.

“Boat C” is that divorce-distressed Trojan 10.8 Meter sale plus the addition of brand new twin 4BY-180 180-hp Yanmar diesels. Complete cost of the hypothetical repower installation was $56,000, including removing the old engines and all costs associated with the wiring, running gear, etc., making the total cost for the boat with the new diesels $95,900.

Huge Fuel Savings with Diesels

The repowered “Boat C” with the 180-hp Yanmar diesels can actually throw far larger props than could the original model with 350-hp gas engines. Powered by gas engines the boat used 16x15 props which were replaced by twin 20x22 props with the new Yanmar diesels. Based on actual test data of similar vessels we estimate that top speed with the new diesels will be about 25 mph and at 20 mph the boat will burn 13 gallons per hour. This compares with the 330-hp gas engines which have a WOT of 29 mph, but burn 31 gallons an hour at 21 mph.

So the new diesels with only 180-hp are only 4 mph slower at WOT but burn about 18 fewer gallons per hour at normal cruising speeds.

The Big Payoff

Our hypothetical “Boat C” Trojan 10.8 Meter costs $18,700 more than, all up, or 24% more than the 22-year old (average) “Boat B”, but has brand new diesels and gets substantially better fuel economy. That fuel savings at $3.50 per gallon ads up to $6300 for every 100 hours of operation at 20 mph over the old gas engines. At that rate, it won’t take many years for the repowered diesels to “pay for themselves” – i.e., defray the cost between the $95,600 and what it would have cost to buy an old boat with old engines – just 300 hours of engine operation could do it!

At the end of the day, we think that repowering with diesel in today’s market will slow what would be a normal depreciation schedule plus pay dividends in fuel savings every time the boat is used.